[css-sizing-4] intrinsic-* does need to actually override intrinsic size, not contribution

[tabatkins]

As written, intrinsic-* only overrides the intrinsic size contribution calculation. But that means that, for example, a <div style="intrinsic-height: 100px;"></div> will be 0 px tall, but will cause a parent element to treat it as 100px tall. That seems wrong! And it means that the contain: size can't really interact with it properly either.

Our fear was that overriding the intrinsic inline size would have interactions with the intrinsic block size, but as far as I can tell none of the layout modes do that. They all calculate inline and block sizes independently.

So we just need to override the intrinsic size itself to use the intrinsic-* properties.